One of the most common types of printers in the field of non-impact printing has been the ink-jet printer. An ink-jet printer emits a stream of ink droplets from an orifice in response to received signals. Several different types of ink-jet printers are known. Chief among these types are printers in which a continuous stream of droplets is emitted from the orifice of the ink jet. Those droplets not required for printing are electrostatically deflected and (typically) recycled for re-emission. Another type of ink-jet printer is the "impulse" type, in which the ink droplets are emitted only in response to print commands. The present invention is applicable to both types of ink-jet printers. In its preferred embodiment, however, the present invention relates to the impulse type of ink-jet printer.
When the performance of a non-impact printer like the ink-jet printer is compared with that of an impact printer, one of the problems encountered with the non-impact machine has been obtaining and maintaining the required control over the printing operation. The related problem of maintaining an adequate supply of ink in the print head, while pulsing the ink fluid to provide droplets of ink in a successive manner during the printing operation, must be overcome to control the impulse ink-jet printing operation. Any ink-jet printer necessarily requires a replenishing of the ink supply and the requirements of the ink-jet printer dictate the design of the ink supply system.
Impulse ink-jet printers which provide droplets of ink on demand in response to the state of energization of a transducer are typically supplied with in from relatively small cartridges because the volume of ink consumed in an impulse ink-jet printer is often relatively small. But certain industrial applications of impulse ink-jet printers require large volumes of ink over extended periods of time. For example, on-line printing of corrugated containers may require a plurality of ink-jet print heads. Each print head has a large number of jets to produce relatively large characters, bar codes, or both. Under these circumstances, a large volume of ink is used for a long time and the use of small cartridges becomes impractical. For printing in this type of application, therefore, a relatively large ink supply is necessary; a container holding 125, 250, 500, or 1000 milliliters may be necessary. The use of such a large ink supply poses certain problems for an impulse ink-jet printer.
First, the process of replenishing the ink supply for an ink-jet printer requires an operator to disconnect the supply from the ink-jet printer and replace the supply. The ink-jet itself, which is relatively expensive, remains permanently mounted on the scanning head of the receiver so as to assure proper droplet placement. One drawback with ink-jet printers in commercial application is the difficulty associated with maintenance of the ink jet and related apparatus (including the ink supply) by relatively unskilled operators or attendants. Accordingly, the operator must be able to install the ink supply into the printing system, by attaching the ink supply to the printer and opening the ink supply to the ink stream, with a minimum of effort.
Often, the ink supply system must be changed before all of the ink contained in the system is used. This usually occurs when the operator wants to assure that the ink supply does not run dry during a printing operation. This may occur, too, if a new color or a different type of ink is required in the application for which the ink-jet printer will be used. Therefore, the ink supply system must permit removal of partially filled containers, without spillage creating a mess, as well as assure an ecologically sound refilling policy.
Third, an impulse ink-jet printer must be primed with ink in order to operate properly. Printing of an impulse ink jet requires that positive pressure be generated in connection with the supply of ink so as to force the ink through the ink-jet chamber and the orifices of the ink jet while preventing ink from being sucked back through the orifices and the chambers upon completion of printing. Accordingly, the ink must dispense from the ink supply smoothly and without interruption to avoid affecting adversely the performance of the printer. The flow of ink must be shut off at some level, of course, to prevent over-filling.
Finally, ink-jet printers must be purged occasionally to remove dried ink or other debris from the orifice or nozzle of the ink jet. Because the orifice or nozzle of the ink jet is extremely small and its size is of the utmost importance in the formation of ink droplets which emerge from the jet, it will be readily appreciated that the orifice must be kept clear of any debris which might interfere with that droplet-forming function. It will further be appreciated that the ink-delivery system for the ink-jet printer must contain ink in a sealed and clean environment devoid of debris. The system must prevent contamination of the ink.
Despite the advantages of ink-jet printers, further commercial acceptance of marking by ink jet awaits improvement of the system by which ink is delivered to the ink-jet printer. Others have attempted to improve ink delivery systems. U.S. Pat. No. 5,343,226 represents one such attempt; the '226 patent is directed to an ink-jet ink supply apparatus. An ink reservoir has a port for releasing ink to a tube which supplies ink jets. The ink is supplied to the reservoir from a container through an opening in the cover of the container. The opening is located in a neck which extends upwardly from the cover and includes threads. The container has a threaded cap which engages the threads on the neck of the cover to attach the container to the ink reservoir. A vent opening (which appears to be permanently open) is provided in the cover.
As best illustrated in FIGS. 9-11 of the '226 patent, a valve mechanism is mounted in the opening in the cover of the container. The valve mechanism interrupts gravity feed of ink from the container into the ink reservoir. A valve actuator or projection is formed in the base of the ink reservoir. A cap projection on the container has an opening which extends into the base and aligns with the actuator. The cap of the container has a plunger which is biased in a closed position by a spring encircling a shaft of the plunger. The valve mechanism is opened automatically, and ink is permitted to flow from the container to the reservoir, when the container is mounted on the base of the reservoir. The spring forces the plunger closed so as to prevent the flow of ink from the container when the container is not mounted on the reservoir base.
The ink-jet ink supply apparatus taught by the '226 patent is relatively complex, expensive, and may be difficult to implement in a variety of applications. Specifically, the apparatus has a number of moving parts--including a spring, plunger, and shaft--which may require maintenance and may fail. Such moving parts also preclude the assurance of repeatable shutoffs. The apparatus stops the flow of ink through a vertical closure action which does not provide a "wiping" action and, therefore, risks ink leakage. Should debris prevent the plunger from seating precisely, an insufficient ink seal might be obtained. In addition, the user must overcome the spring force to screw the ink supply apparatus to the ink-jet printer. Finally, removing a partially filled bottle of ink may cause leakage because the bottle must be largely unthreaded before the valve closes.
Industrial ink-jet applications require specialized ink delivery systems. To overcome the shortcomings of existing impulse ink-jet ink delivery systems, a new ink-jet bottle and valve system is provided. An object of the present invention is to provide a large ink supply for an impulse ink-jet printer which can be removed from that printer. Another object is to provide an ink delivery system that contains ink in a sealed and clean environment. A related object is to provide a system that prevents contamination of ink. Yet another object is to provide a system which is reliable, easy to use, and avoids material compatibility problems.
It is still another object of the present invention to substantially eliminate the possibility of any spillage of ink. An additional object is to provide an ink delivery system which is entirely compatible with existing ink-jet printers. A related object is to provide a system which dispenses ink without affecting the performance of the printer. Yet another related object of this invention is to provide a system that, when installed into the ink-jet printer, attaches to the printer and opens to the ink stream with a um of operator effort. An additional object is to provide a valve system which closes fully before the bottle disengages from the reservoir, thereby preventing spillage of ink during bottle removal.